Topic: Sagittarius A*

This Nature Podcast episode reports on a high-speed star whose orbit could enable measurement of the spin of Sagittarius A*, the supermassive black hole at the centre of the Milky Way. The programme also examines how exoskeletons influence human movement and covers other current science stories.

How can black holes be established both as a consequence of gravitational theory and as objects in the sky? Roger Penrose examines the mathematical development of gravitational collapse and space-time singularities, explaining why black-hole formation does not depend on perfectly symmetric idealisations. Reinhard Genzel and Andrea Ghez trace the observational effort to establish a massive compact object at the centre of the Milky Way. Their accounts connect infrared observations, improvements in imaging through atmospheric distortion, and long-term measurements of stellar motions around Sagitt